As is known, there are a variety of types of magnetic field sensing elements, including, but not limited to, Hall Effect elements, magnetoresistance elements, and magnetotransistors. As is also known, there are different types of Hall Effect elements, for example, planar Hall elements, vertical Hall elements, and circular Hall elements. As is also known, there are different types of magnetoresistance elements, for example, anisotropic magnetoresistance (AMR) elements, giant magnetoresistance (GMR) elements, tunneling magnetoresistance (TMR) elements, Indium antimonide (InSb) elements, and magnetic tunnel junction (MTJ) elements.
Hall Effect elements generate an output voltage proportional to a magnetic field. In contrast, magnetoresistance elements change resistance in proportion to a magnetic field. In a circuit, an electrical current can be directed through the magnetoresistance element, thereby generating a voltage output signal proportional to the magnetic field.
Magnetic field sensors, which use magnetic field sensing elements, are used in a variety of applications, including, but not limited to, a current sensor that senses a magnetic field generated by a current carried by a current-carrying conductor, a magnetic switch, a proximity detector that senses the proximity of a ferromagnetic or magnetic object, a rotation detector that senses passing ferromagnetic articles, for example, gear teeth, and a magnetic field sensor that senses a magnetic field density of a magnetic field. Magnetic switches are used as examples herein. However, the circuits and techniques described herein apply also to any magnetic field sensor.
It is known that Hall Effect elements exhibit an undesirable DC offset voltage. Techniques have been developed to reduce the DC offset voltage, while still allowing the Hall Effect element to sense a DC magnetic field. One such technique is commonly referred to as “chopping” or “current spinning” and entails driving a Hall Effect element in two or more different directions and receiving output signals at different output terminals as the Hall Effect element is differently driven. In this way, selected drive and signal contact pairs are interchanged during each phase of the chopping and offset voltages of the different driving arrangements tend to cancel toward zero.
Chopping is also a well-known technique applied to amplifiers to reduce an offset component and low frequency noise (i.e., flicker noise) of signals applied to the amplifier. Amplifiers implementing chopping are often referred to as chopper stabilized amplifiers.
Chopping tends to generate undesirable spectral components (i.e., frequency components in the frequency domain) and ripple in the resulting signal, which spectral components and ripple can be removed with filters. While conventional arrangements that use filters can effectively reduce the ripple, it will be understood that the filters tend to reduce a bandwidth or a response time of the magnetic field sensor.